2008-04-16 20:28:51

by Jeff Layton

[permalink] [raw]
Subject: [PATCH 1/2] knfsd: get rid of imode variable in nfsd_setattr

...it's not really needed.

Signed-off-by: Jeff Layton <[email protected]>
---
fs/nfsd/vfs.c | 4 +---
1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 17ac51b..dd4dcb4 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -264,7 +264,6 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
struct inode *inode;
int accmode = MAY_SATTR;
int ftype = 0;
- int imode;
__be32 err;
int host_err;
int size_change = 0;
@@ -360,10 +359,9 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
DQUOT_INIT(inode);
}

- imode = inode->i_mode;
if (iap->ia_valid & ATTR_MODE) {
iap->ia_mode &= S_IALLUGO;
- imode = iap->ia_mode |= (imode & ~S_IALLUGO);
+ iap->ia_mode |= (inode->i_mode & ~S_IALLUGO);
/* if changing uid/gid revoke setuid/setgid in mode */
if ((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid) {
iap->ia_valid |= ATTR_KILL_PRIV;
--
1.5.3.6



2008-04-17 21:47:48

by [email protected]

[permalink] [raw]
Subject: Re: [PATCH 2/2] knfsd: clear both setuid and setgid whenever a chown is done

Thanks for the extra explanation--I've applied both.

--b.

On Wed, Apr 16, 2008 at 04:28:47PM -0400, Jeff Layton wrote:
> Currently, knfsd only clears the setuid bit if the owner of a file is
> changed on a SETATTR call, and only clears the setgid bit if the group
> is changed. POSIX says this in the spec for chown():
>
> "If the specified file is a regular file, one or more of the
> S_IXUSR, S_IXGRP, or S_IXOTH bits of the file mode are set, and the
> process does not have appropriate privileges, the set-user-ID
> (S_ISUID) and set-group-ID (S_ISGID) bits of the file mode shall
> be cleared upon successful return from chown()."
>
> If I'm reading this correctly, then knfsd is doing this wrong. It should
> be clearing both the setuid and setgid bit on any SETATTR that changes
> the uid or gid. This wasn't really as noticable before, but now that the
> ATTR_KILL_S*ID bits are a no-op for the NFS client, it's more evident.
>
> This patch corrects the nfsd_setattr logic so that this occurs. It also
> does a bit of cleanup to the function.
>
> There is also one small behavioral change. If a SETATTR call comes in
> that changes the uid/gid and the mode, then we now only clear the setgid
> bit if the group execute bit isn't set. The setgid bit without a group
> execute bit signifies mandatory locking and we likely don't want to
> clear the bit in that case. Since there is no call in POSIX that should
> generate a SETATTR call like this, then this should rarely happen, but
> it's worth noting.
>
> Signed-off-by: Jeff Layton <[email protected]>
> ---
> fs/nfsd/vfs.c | 27 ++++++++++++++-------------
> 1 files changed, 14 insertions(+), 13 deletions(-)
>
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index dd4dcb4..f092b53 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -359,24 +359,25 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
> DQUOT_INIT(inode);
> }
>
> + /* sanitize the mode change */
> if (iap->ia_valid & ATTR_MODE) {
> iap->ia_mode &= S_IALLUGO;
> iap->ia_mode |= (inode->i_mode & ~S_IALLUGO);
> - /* if changing uid/gid revoke setuid/setgid in mode */
> - if ((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid) {
> - iap->ia_valid |= ATTR_KILL_PRIV;
> + }
> +
> + /* Revoke setuid/setgid on chown */
> + if (((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid) ||
> + ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)) {
> + iap->ia_valid |= ATTR_KILL_PRIV;
> + if (iap->ia_valid & ATTR_MODE) {
> + /* we're setting mode too, just clear the s*id bits */
> iap->ia_mode &= ~S_ISUID;
> + if (iap->ia_mode & S_IXGRP)
> + iap->ia_mode &= ~S_ISGID;
> + } else {
> + /* set ATTR_KILL_* bits and let VFS handle it */
> + iap->ia_valid |= (ATTR_KILL_SUID | ATTR_KILL_SGID);
> }
> - if ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)
> - iap->ia_mode &= ~S_ISGID;
> - } else {
> - /*
> - * Revoke setuid/setgid bit on chown/chgrp
> - */
> - if ((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid)
> - iap->ia_valid |= ATTR_KILL_SUID | ATTR_KILL_PRIV;
> - if ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)
> - iap->ia_valid |= ATTR_KILL_SGID;
> }
>
> /* Change the attributes. */
> --
> 1.5.3.6
>

2008-04-16 20:28:47

by Jeff Layton

[permalink] [raw]
Subject: [PATCH 2/2] knfsd: clear both setuid and setgid whenever a chown is done

Currently, knfsd only clears the setuid bit if the owner of a file is
changed on a SETATTR call, and only clears the setgid bit if the group
is changed. POSIX says this in the spec for chown():

"If the specified file is a regular file, one or more of the
S_IXUSR, S_IXGRP, or S_IXOTH bits of the file mode are set, and the
process does not have appropriate privileges, the set-user-ID
(S_ISUID) and set-group-ID (S_ISGID) bits of the file mode shall
be cleared upon successful return from chown()."

If I'm reading this correctly, then knfsd is doing this wrong. It should
be clearing both the setuid and setgid bit on any SETATTR that changes
the uid or gid. This wasn't really as noticable before, but now that the
ATTR_KILL_S*ID bits are a no-op for the NFS client, it's more evident.

This patch corrects the nfsd_setattr logic so that this occurs. It also
does a bit of cleanup to the function.

There is also one small behavioral change. If a SETATTR call comes in
that changes the uid/gid and the mode, then we now only clear the setgid
bit if the group execute bit isn't set. The setgid bit without a group
execute bit signifies mandatory locking and we likely don't want to
clear the bit in that case. Since there is no call in POSIX that should
generate a SETATTR call like this, then this should rarely happen, but
it's worth noting.

Signed-off-by: Jeff Layton <[email protected]>
---
fs/nfsd/vfs.c | 27 ++++++++++++++-------------
1 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index dd4dcb4..f092b53 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -359,24 +359,25 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
DQUOT_INIT(inode);
}

+ /* sanitize the mode change */
if (iap->ia_valid & ATTR_MODE) {
iap->ia_mode &= S_IALLUGO;
iap->ia_mode |= (inode->i_mode & ~S_IALLUGO);
- /* if changing uid/gid revoke setuid/setgid in mode */
- if ((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid) {
- iap->ia_valid |= ATTR_KILL_PRIV;
+ }
+
+ /* Revoke setuid/setgid on chown */
+ if (((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid) ||
+ ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)) {
+ iap->ia_valid |= ATTR_KILL_PRIV;
+ if (iap->ia_valid & ATTR_MODE) {
+ /* we're setting mode too, just clear the s*id bits */
iap->ia_mode &= ~S_ISUID;
+ if (iap->ia_mode & S_IXGRP)
+ iap->ia_mode &= ~S_ISGID;
+ } else {
+ /* set ATTR_KILL_* bits and let VFS handle it */
+ iap->ia_valid |= (ATTR_KILL_SUID | ATTR_KILL_SGID);
}
- if ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)
- iap->ia_mode &= ~S_ISGID;
- } else {
- /*
- * Revoke setuid/setgid bit on chown/chgrp
- */
- if ((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid)
- iap->ia_valid |= ATTR_KILL_SUID | ATTR_KILL_PRIV;
- if ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)
- iap->ia_valid |= ATTR_KILL_SGID;
}

/* Change the attributes. */
--
1.5.3.6